Development inhibitor releasing compounds or couplers (DIR's) are compounds that release development inhibitor compounds upon reaction with oxidized developer. DIR's are used in photographic materials to improve image sharpness (acutance), reduce gamma-normalized granularity (a measure of signal to noise ratio with a low gamma-normalized granularity indicating a beneficial high signal to noise ratio), control tone scale, and control color correction.
It is often desirable to maximize the amount of development inhibitor that is released in order to maximize the amount of sharpness and minimize the contrast(gamma)-normalized granularity of the image produced in a photographic material. However, the amount of tone scale control and color correction control must usually be maintained within specific limits for visually pleasing image reproduction. This often limits the degree of sharpness and gamma-normalized granularity improvement that can be obtained through the use of DIR compounds.
This problem has been addressed in a number of ways. One way to increase image sharpness provided by a DIR compound is to increase the effective mobility of the released inhibitor compound by linking it to a coupler moiety through a timing group. Upon reaction with oxidized developer, the timing-inhibitor moiety is cleaved from the coupler moiety. The inhibitor moiety releases from the timing group and thus becomes active, but only after a delay during which the timing-inhibitor moiety could move in the material. The incorporation of such timing groups in DIR's and the advantages thereby achieved is described in U.S. Pat. Nos. 4,284,962 and 4,409,323. An example of such a timed DIR is: ##STR1##
Another technique is to limit the amount of color correction, the so-called interimage effect, by utilizing a DIR that releases an inhibitor moiety that comprises a ballasting group enabling, upon exposure and processing of the material, reduced interlayer interimage effect without reduced image acutance. Such DIR's are described in the U.S. Patent Application entitled, "Photographic Materials and Process", filed concurrently herewith in the names of R. P. Szajewski, J. N. Poslusny, and W. K. Slusarek. These DIR's, however, do not provide reductions in gamma-normalized granularity to the extent that is often desirable.
It would therefore be highly desirable to provide a photographic material that offered the concommitant advantages of high image sharpness, low interlayer interimage effect, and low gamma-normalized granularity.
In an unrelated area, it has been taught to incorporate bleach accelerator-releasing compounds (BARC's) in photographic materials to aid in the bleaching step of photographic processing. European Patent Application Publication No. 193,389 discloses BARC's having a releasable thioether bonded to an alkylene group or heterocyclic nucleus with a solubilizing group attached thereto. One such BARC, having the formula: ##STR2## has been used as such in a color negative film, which also contained the above-identified DIR, D-1. This DIR does not have a --CH.sub.2 --Q ballasting group. This combination, as shown below by comparative data, did not provide as great a reduction in gamma-normalized granularity (as compared to the DIR alone) as might be desired.
It has now been found that a specific subset of a class of compounds previously believed to be useful only as BARC's, allows for the incorporation of greater amounts of DIR's while maintaining the degree of color correction, and can provide the advantages of low interlayer interimage effect, high image sharpness, and low gamma-normalized granularity when used in combination with the above-described ballasted inhibitor-releasing compounds.